I am looking for a tool that is either Web- or Windows-based that will
find all the domains that are owned by a given contact. For example,
if I go to Network Solutions I can type in a domain name and find the
NIC handle of the person or corporation that owns that domain. I then
want to find ALL the domains associated with that NIC handle. I would
like to do some research on entities that own multiple domains, and I
would like to be able to do as many searches as I like. Obviously, a
free tool would be ideal.

Hi there,

I have found four ways of achieving your task.

1) Dialog Select
http://openaccess.dialog.com/ip/

Click on domain names in the left column and you will get to a form
for searching Whois by owner names. It costs $3.65 to view each
record.

2) Saegis
http://www.compu-mark.com/Frameset.asp?reference=03-01.02-01.03-01&lang=en&country=0

Subscribers can look up domains by owner for roughly $1 per record,
although it doesn't mention it on their site. Details here:
http://ttdomino.thomson-thomson.com/www/NewProducts.nsf/8bb1fd719a941393852569220043a2d8/cea045c57bee6e4785256b3a005e1554?OpenDocument

3)MarkMonitor
http://www.markmonitor.com/
Subscription based. Also available via Lexis Nexis

4)Verisign Referral LDAP
http://www.ldap.verisignlabs.com/

Click on Organization to search for a name, and find out the domains
they own. Only works for domains registered via Verisign.

Best wishes,
robertskelton-ga

Outstanding! The Verisign Referral LDAP was exactly what I needed!
This was my first Google Answers experience and now I am hooked!